Spur gears are the most typical kind of gears. They possess straight teeth, and are installed 
on parallel shafts. Occasionally, many spur gears are utilized simultaneously to create very large gear reductions.
Spur gears are used in many products that you can see all over HowStuffWorks, like the electric screwdriver, dancing monster, oscillating sprinkler, windup noisy alarms, washing machine and clothes dryer. Nevertheless, you won’t discover many in your vehicle.
This is because the spur gear could be really loud. Each time a gear tooth engages a tooth on the other gear, the teeth collide, and this impact makes a sound. In addition, it increases the pressure on the gear teeth.
To China Pulley reduce the noise and stress in the gears, the majority of the gears in your vehicle are helical.